Fabrics of melt-blown polymeric fibers are well known and are used to separate fine particles from air and cooking oils and oil-based materials from oil-water mixtures, e.g., as in crude oil water spills, as is well known in the art (see U.S. Pat. Nos. 3,764,527, 4,011,067 and 4,604,203). Nonwoven webs have also been referred to as melt blown polymer fibers (see British Patent No. 2,113,731) and as blown microfibers (see U.S. Pat. No. 3,971,373).
Spunbonded webs have been used for filtration and have been disclosed, for example, in U.S. Pat. Nos. 3,338,992, 3,509,009, and 3,528,129. The '509 patent discloses applying charcoal to the filaments. A process for preparing air-laid webs is disclosed in U.S. Pat. No. 3,991,526.
U.S. Pat. Nos. 5,029,699 and 4,933,229 disclose sorbent packaging materials for liquid-containing bottles. The materials were melt-blown compressed polyolefin.
Loading of sorptive particulates in nonwoven webs (sometimes also referred to as blown microfibers) is also well known in the art and disclosed in UK Patent GB 2113731, U.S. Pat. Nos. 3,971,373, 4,433,024, 4,469,734, 4,797,318, and 4,957,943. Utilities include face respirators for removing particulates and gaseous contaminants, protective garments, fluid retaining articles, and wipers for oil.
A method is disclosed in European Patent Application No. 0 080 382) by which particles are retained by mechanical entanglement by being brought into contact with fibers while the fibers are still in a tacky condition. "The particles in the resulting fabric web are held firmly even if the fabric is abraded or torn when used as a wiper". This was explained in this reference which states: "The particles of super absorbent material have relatively large diameter compared to the diameter of the individual microfibers and thus tend to be trapped within a network of the fibers and therefore little surface tack of the fibers is needed to maintain the super absorbent particles in place".
U.S. Pat. No. 4,429,001 teaches a sorbent sheet product comprising a coherent web of entangled melt blown fibers and an array of solid high-sorbency liquid sorbent polymeric materials uniformly dispersed and physically held within the web, the particles swelling upon sorption of liquid and the web expanding as the particles swell. The product rapidly absorbs and retains large quantities of liquid.
Many of the prior known nonwoven webs have shortcomings, among them being poor or low particulate loading capabilities. In some cases particulates must be large, e.g., greater than 100 micrometers, to be trapped mechanically within a web, and formed webs often have poor physical properties, such as lack of strength.
U.S. Pat. No. 4,684,570 teaches fuse bonding of conjugate fibers to provide a water impervious laminated material wherein cores of the conjugate fibers retain their initial fiber-like integrity. The laminated material is useful as an absorbent disposable drape which is impermeable to the passage of microorganisms and fluids.
To increase the strength of melt-blown polymeric fibers containing absorbent particles adhering to the fibers, British Patent No. 2,113,731 teaches hot calendaring or embossing with heated, patterned bonding rolls. The product is a fluid retentive nonwoven web.
High surface area particulate are known to be useful in separation processes such as extraction and chromatography. Columns of particulate such as nylon, alumina, zirconia, and silica, can provide a means of separating and analyzing mixtures by selective sorption. The process is based on differences in the distribution ratios of components of mixtures between a mutually immiscible mobile and fixed stationary phase. The resultant separated components of mixtures can be further examined.
Chromatographic articles comprising a fibrillated polytetrafluoroethylene matrix having enmeshed therein sorptive particulate have been disclosed, for example, in U.S. Pat. Nos. 4,460,642, 4,810,381, 4,906,378, 4,971,736, 4,971,697, U.S. Ser. No. 07/639,515 filed Jan. 10, 1991, now U.S. Pat. No. 5,071,610.